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Wally Peck: Keep an eye on the herbicides

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The phone call went something like this: "Last spring I bought new starter mix and planted my tomato seeds like I usually do. Very few germinated and the seedlings that came up died. What did I do wrong?"

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Last year, there were many questions like that in periodicals, extension offices and at online sites. More and more problems like this have been traced to herbicide contamination of bagged mixes, compost and soils.

One person talked about putting a load of composted cow manure on new garden beds and around fruit trees. The beds exhibited "bizarre growth" and the fruits exhibited leaf curl. It turns out that the composted manure was contaminated with aminoprylid, an herbicide used to control broadleaf weeds in grazing land. This herbicide persists even after going through the cattle and after hot composting.

A golf course in the Twin Cities filed a lawsuit after pine and spruce trees died after an application of Dupont Imprelis herbicide was used to kill broadleaf weeds and clover in the grass. Lawsuits are extending into many states and by homeowners and tree farmers who had damage to trees after the herbicide was applied. Wood chips ground from affected trees used in gardens and landscapes have also exhibited the same effects.

First sold in October 2010, the active ingredient in the herbicide is aminocyclopyrachlor, a potent herbicide that persists in grass clippings and wood chips from treated areas. Unfortunately, in Minnesota homeowners cannot have material tested by the Minnesota Department of Agriculture for suspected contamination.

Three other herbicides notorious for persisting in dead plants and compost are copyralid, picloram and triclopyr. They are commonly used to control broadleaf weeds such as thistle, burdock and woody plants in rights of way and abandoned areas. Some are only available to licensed applicators but are readily available on the black market. Some are components of woody herbicides sold over the counter.

If you use "weed killers," look at the label to see what the active herbicide is. Sometimes the cautions are buried on page seven of a nine-page label. If you use a lawn service, ask for a printed copy of the ingredients of what is sprayed or applied to your lawn. Look for those chemicals in the listing.

Many people buy bagged starter mix, compost, manure, potting soil or mulch. At this point, there is no way of knowing what was used to prepare these products because there is no regulation about labeling non-food items. Never mind that they may be used to raise food. My advice is to stick with reputable companies and even call to ask if the product has been tested for contamination.

I hope that in the future compost and soils sold to homeowners will be certified to be herbicide free. But homeowners and gardeners still are on their own without resources to ascertain product safety.

Master Gardeners will answer your gardening questions via a voice-mail service. Call 444-7916, leaving your phone number, name and the nature of your question. A master gardener will give you a call to speak with you personally. Find horticultural information on the University of Minnesota Extension website at

www.extension.umn.edu/gardeninfo/

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